+/* This patch should work ONLY with YUY2 image formats, also known as YUYV or
+ * YUV422 formats.
+ * This patched function allows to overturn video images from an upside-down
+ * orientation to a normal one. The conversion consists in copying 4 bytes at a
+ * time (Y0,U0,Y1,V0) corresponding to 2 pixels from the frame (coming from the
+ * video source) to the buffer that will be used by the application requesting
+ * the video stream. But in order to satisfy the YUY2 image format byte has to
+ * be copied in this way: Y1 U0 Y0 VO. Bytes are copied in a bottom-up
+ * direction into the reversed frame.
+ * “data” stores a sequence of pixels coming from the video source.
+ * This sequence is not a full frame or a full row of pixel, but just an
+ * ordered vector of pixels (from top-left to bottom-right), whose
+ * represents just an area of the current frame and which size (“nbytes”) is
+ * not constant. In fact this function has to be called hundreds of times
+ * before a frame is completed. Each time “data” contains the next part of the
+ * current frame (upside-down). At the end data stored in “mem” buffer will be
+ * used by the application who requested the video stream.
+ * No memory allocation is needed because pixel order is modified directly
+ * while copying from “data” into “mem” buffer (i.e. in each call of this
+ * function), and not just once when the frame is already completed.
+ */
static void uvc_video_decode_data(struct uvc_video_device *video,
struct uvc_buffer *buf, const __u8 *data, int len)
{
struct uvc_video_queue *queue = &video->queue;
unsigned int maxlen, nbytes;
void *mem;
+ /* Patch variables */
+ unsigned int i, pixel_size;
+ __u8 *ptr_tmp;